National Center for Immunization & Respiratory Diseases

Influenza Vaccine Safety Update and 

Proposed Recommendations for the 2023-24 Influenza Season

Lisa A. Grohskopf

Influenza Division, CDC/NCIRD

Advisory Committee on Immunization Practices

June 21, 2023
Influenza Division

• Lenee Blanton

• Jill Ferdinands

• Lindsay Trujillo

• Lynette Brammer

• Alicia Budd

• Jessie Chung

• Brendan Flannery

• Sinead Morris

• Samantha Olson

• Sascha Ellington

• Carrie Reed

• Mark Tenforde

• Tim Uyeki

Immunization Safety Office

• Geta Aynalem

• Karen Broder

• Pedro Moro

• Elaine Miller

• Shashi Sharma

• David Shay

• Tom Shimabukuro

Immunization Services Division

• Andrew Kroger

CDC Library

• Joanna Taliano

CISA

• Donna Hummell

Acknowledgements
Influenza Vaccine Safety Update
Vaccine Safety Update: 2022-2023 Influenza Season 

▪ ~173 million doses of influenza vaccine distributed in United States* 

▪ Vaccine Adverse Event Reporting System (VAERS) (co-managed by CDC and FDA) 

• No new safety concerns identified for influenza vaccines 

▪ Vaccine Safety Datalink (VSD) (collaboration between CDC and 9 integrated healthcare 

organizations)

• ~5.5 million doses of influenza vaccine administered in VSD

• No new safety concerns identified in influenza vaccine monitoring** 

• Statistical signal for ischemic stroke after Pfizer-BioNTech bivalent mRNA COVID-19 vaccine in persons 

aged ≥65 years detected in VSD analysis for COVID-19 vaccine safety monitoring, previously presented 

to ACIP***

• Post-signal analysis in VSD found an elevated rate ratio for ischemic stroke after simultaneous vaccination with 

Pfizer-BioNTech bivalent mRNA COVID-19 vaccine and high-dose or adjuvanted influenza vaccine, which has 

attenuated over time

• Separate analyses did not detect an elevated rate ratio for ischemic stroke after influenza vaccine administered 

without bivalent mRNA COVID-19 vaccine

4

* Weekly Flu Vaccination Dashboard | FluVaxView | Seasonal Influenza (Flu) | CDC

** Outcomes monitored in VSD: acute disseminated encephalomyelitis, anaphylaxis, Bell’s Palsy, encephalitis, Guillain-Barré syndrome, seizures, transverse myelitis 

*** Shimabukuro T, ACIP presentation on April 19, 2023 mRNA COVID-19 bivalent booster vaccine safety update (cdc.gov)
Overview of Proposed Recommendations for 

2023-24
• Vaccination of all persons aged ≥6 months who do not have contraindications 

continues to be recommended.

• Recommendations regarding timing of vaccination are unchanged from 2022-23.

• Changes include:

– Updated U.S. influenza vaccine composition for 2023-24.

– Proposed changes to the recommendations for vaccination for persons with egg 

allergy.

Overview of Proposed Recommendations
Timing of Vaccination
• Unchanged from last season.

• For most persons who need only 1 dose of influenza vaccine for the season, 

vaccination should ideally be offered during September or October.

• Vaccination should continue after October and throughout the influenza season as 

long as influenza viruses are circulating and unexpired vaccine is available.

• Vaccination during July and August are not recommended for most groups.

• Considerations for July and August vaccination are noted for adults, children, and 

pregnant persons.

Timing of Influenza Vaccination
• For most adults (particularly adults aged ≥65 years) and for pregnant persons in the 

first or second trimester, vaccination during July and August should be avoided 

unless there is concern that vaccination later in the season might not be possible.

Timing of Influenza Vaccination—

Adults and Pregnant Persons in First/Second Trimester
• Children who require 2 doses: 

– Should receive their first dose as soon as possible (including during July and 

August, if vaccine is available) to allow the second dose (which must be 

administered ≥4 weeks later) to be received, ideally, by the end of October.

• Children who require only 1 dose: 

– Vaccination during July and August can be considered for children of any age 

who need only 1 dose of influenza vaccine for the season. 

Timing of Influenza Vaccination—

Children
• Vaccination during July and August can be considered because vaccination might 

reduce risk for influenza illness in their infants during the first months after birth, 

when they are too young to receive influenza vaccine.

Timing of Influenza Vaccination—

Pregnant Persons in Third Trimester
Influenza Vaccine Composition for 2023-24
• All vaccines available in the U.S. are quadrivalent.

• The 2023-24 composition includes updated influenza A(H1N1)pdm09 components.

• All U.S.-licensed influenza vaccines will include hemagglutinin derived from:

– An influenza A/Victoria/4897/2022 (H1N1)pdm09-like virus (egg-based vaccines) 

An influenza A/Wisconsin/67/2022 (H1N1)pdm09-like virus (cell and recombinant vaccines)

– An influenza A/Darwin/9/2021 (H3N2)-like virus (egg-based vaccines)

An influenza A/Darwin/6/2021 (H3N2)-like virus (cell and recombinant vaccines)

– An influenza B/Austria/1359417/2021-like virus (B/Victoria lineage)

– An influenza B/Phuket/3073/2013-like virus (B/Yamagata lineage)

U.S. Influenza Vaccine Composition for 2023-24

Vaccines and Related Biological Products Advisory Committee March 7, 2023 Meeting Announcement - 03/07/2023 | FDA
Proposed Recommendations for Vaccination of 

Persons with Egg Allergy
• All persons aged ≥6 months with egg allergy should receive influenza vaccine unless a 

contraindication exists. Any influenza vaccine that is otherwise appropriate for the recipient’s age and 

health status can be used (egg based or non-egg based). 

• Egg allergy in and of itself necessitates no additional safety measures for influenza vaccination 

beyond those recommended for any recipient of any vaccine, regardless of severity of previous 

reaction to egg.

• Severe and life-threatening reactions to vaccines can rarely occur with any vaccine and in any vaccine 

recipient, regardless of allergy history. Providers are reminded that all vaccines should be 

administered in settings in which personnel and equipment needed for rapid recognition and 

treatment of acute hypersensitivity reactions are available. All vaccination providers should be 

familiar with their office emergency plan and be certified in cardiopulmonary resuscitation.

Proposed Recommendations for Vaccination of 

Persons with Egg Allergy
For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.